This invention relates to novel copolyetherketone compositions of matter, to processes for making them, to shaped articles and composite structures prepared from them and to blends of them with other polymers.
Copolymers of aromatic diacid chlorides with diphenyl ether are known in the art. (Such copolymers will be termed "copolyetherketones" in this application). U.S. Pat. Nos. 3,516,966 and 3,637,592, issued to Berr on June 23, 1970, and Jan. 25, 1972, respectively, disclose copolyetherketones having the following repeating structural unit ##STR1## where the ##STR2## moiety is either ##STR3## Both patents disclose that the copolyetherketones may be prepared by combining diphenyl ether and a mixture of terephthalyl halide and isophthalyl halide with a Friedel-Crafts catalyst such as boron trifluoride. Further process refinements, and the use of different catalysts, are described in U.S. Pat. No. 3,767,620, issued Oct. 23, 1973, and in U.S. Pat. No. 3,791,890, issued Feb. 12, 1974.
Most commercial applications for copolyetherketones require resins having high molecular weight. Thermoplastic processing applications, such as extrusion, injection molding, and film and sheet forming require a high degree of melt strength during the processing step, and melt strength increases with molecular weight. High molecular weight is also needed for fabrication by sintering processes where free forms are coalesced by heat treatment without pressure. Thus, the ability to increase and control the molecular weight of copolyetherketones is essential to their use.
Heretofore, it has been difficult to attain copolyetherketones of high molecular weight. An obstacle to preparing high molecular weight copolyetherketones of this type is the formation of xanthydrol "dead ends" in the polymer chain when an acid chloride attacks one ring of a previously unreacted diphenylether molecule in an ortho-position followed by ring closure: ##STR4## See, for example U.S. Pat. No. 3,767,620, issued Oct. 23, 1973, where the presence of these 9-phenyl xanthydrol end groups is reported.
One way to attain higher molecular weight copolyetherketones is to control the generation of xanthdyrol in the process for their manufacture. This can be done by preparing the intermediate oligomer (2 moles diphenyl ether and 1 mole aromatic diacid chloride) and isolating and purifying that oligomer, by recrystallization, prior to polymerization. This purification step allows one to produce very high molecular weight polymers; however, since the overall process involves two separate steps, its cost makes it unacceptable as a route to commercial quantities of copolyetherketones.
GB Pat. No. 2 138 433A (published Oct. 24, 1984) suggests a process for producing poly(arylene ketones) in which side reactions such as ortho-substitution, alkylation and chain branching are alleged to be suppressed so as to produce high molecular weight, essentially linear polymers. The process comprises polymerizing (1) phosgene or an aromatic diacid dihalide together with a polynuclear aromatic comonomer containing two active hydrogen atoms or (ii) a polynuclear aromatic comonomer containing both an acid halide group and an active hydrogen atom, in the presense of a Lewis acid, optionally a controlling agent (usually a Lewis base) and optionally a non-protic diluent.
There is thus a need for copolyetherketones of high molecular weight that can be prepared by commercially feasible processes.